Personal authentication systems using biological information, such as fingerprints, have recently been commercially available. The biological information utilizes, for example, a fingerprint, a palm print, a finger shape, a palm shape, voice, a retina, an iris, a face image, a dynamic signature, blood-vessel arrangements, or keystroke. The biometric information is superior in reliability to a password. Of biometric information, a fingerprint is used frequently.
In a personal authentication system using a fingerprint, a fingerprint is to be checked against all sample fingerprints by means of round-robin matching. For instance, the authentication system employs a matching method (matching technique) of so-called one-fingerprint-against-multiple-registered-fingerprints type (hereinafter simply called a “1-N fingerprint matching method”). Round-robin matching is a technique of checking a fingerprint against all the registered fingerprint data for matching purpose, in sequence from the top. If fingerprint data pertaining to a person of interest are coincidentally located at the head of the sequence, it is expected that matching processing can be terminated immediately without involvement of matching operation using a fingerprint pattern.
With regard to personal authentication using a fingerprint, various systems have so far been developed which, instead of the old-established method involving visual inspection, a laser, etc. is used and a pattern is inputted into a computer as an image and analyzed. A large number of techniques for a sensor section for detecting a fingerprint have been proposed; for example, an optical method in which a fingerprint pattern is directly captured into an image sensor by combining differences in scattering angle between peak and valley with total reflection conditions, and a method in which a pattern is extracted by utilizing a semiconductor sensor that detects differences in charge distribution on a contact face have been put into practice. Furthermore, a method in which personal authentication is carried out by extracting a vein pattern of a finger-tip or a palm of a hand by means of near-infrared light has been proposed.